If you purchase something that only has a model number but no trademark, there are the following ways to deal with it:

* Negotiate with the seller or manufacturer. First, you should contact the seller or manufacturer as soon as possible and clearly inform them of the lack of trademark. During the communication process, you must express your position and requirements, including your wish to return or exchange goods.

* Seek help from consumer associations. If the negotiation fails, you can choose to complain to the consumer association. After receiving a complaint, the Consumer Association will transfer the reported issues to the unit being complained for, and the unit being complained will need to handle and respond within the specified time.

It should be noted that when purchasing goods, you should carefully check the identification and labels of the goods to ensure that the goods purchased are regular and legal goods. If there is no trademark, you need to be vigilant. It may be a counterfeit or other illegal product. It is recommended to take timely measures to protect your rights and interests.